Filtering facemasks or respirators are widely used to protect the user from inhaling dust or chemical particles, depending on the filter properties and certifications. However, wearing a respirator for prolonged periods causes discomfort to the user, due to the build-up of hot air, moisture and carbon dioxide within the respirator. As the time progress, the moisture build-up will also block the filter material, making it more difficult for the user to breathe.
To mitigate these issues, unidirectional valves are commonly installed to respirators. There are different types of valve concepts and membranes or flaps used in the respirators. The basic concept is to allow exhausting of warm, moist exhaled air from the interior space of the respirator, when the flap opens upon exhalation. Conversely, the flap closes upon inhalation, preventing ambient air and particles from entering into the interior of the respirator. However, these valves have limited effectiveness and do not allow exhalation to be purged fast enough. This is even more apparent if the internal space of the respirator is large resulting in more dead space, or if the wearer has shallow breathing which may not be strong enough to open the membrane or flap wide.
Most of the respirators are installed with a Powered Air Purifying Respirators (PAPR) comprising a blower for supplying air from the exterior of the respirator into the respirator. Such blowers provide positive air-flow, or supply air to the wearer. Some respiratory device use Active Venting System (AVS) for example, comprising a blower and electronics in a plastic housing, for sucking out warm, moist air from the internal space of respirator. The AVS works differently from PAPR, as it does not supply air into the respirator, but rather sucks air out from the interior of the respirator to provide air exchange.
Thus, the respirators are usually installed with either unidirectional valve or AVS or PAPR systems to allow air exchange inside the respirator. AVS are comfortable under prolong use and suitable for general public compared to PAPR system. The respirator with unidirectional valve alone does not allow exhalation to be purged fast enough. Also, the respirators installed with AVS alone may not prevent ambient air from flowing in, when the AVS runs out of battery and/or stop operating.
A need, therefore, exists for an improved unidirectional valve with the feature of enabling an electronic blower to be attached onto it, to overcome the above drawbacks.